Biomedical subjects

K Brewer

Publications and source records attributed to K Brewer.

At least 19 recordsLinked to original sources

PubMed1991

Combined administration of a gonadotropin-releasing hormone antagonist and testosterone in men induces reversible azoospermia without loss of libido.

GnRH antagonists suppress pituitary and gonadal function by competing with endogenous GnRH for binding to receptors on pituitary gonadotrophs. We studied the effects of GnRH antagonist administration to men in a protocol simulating a likely male contraceptive regimen combined with a low dose of testosterone. The GnRH antagonist Nal-Glu was given daily (10 mg, sc) for 20 weeks to eight normal men, and a low dose of testosterone enanthate (25 mg, sc) was given every week. Sperm counts started declining during week 4, and complete azoospermia was reached within 6-12 weeks in six of the eight subjects. Subjects 7 and 8, whose sperm counts and serum gonadotropin levels were not suppressed after 10 weeks, were given 20 mg Nal-Glu starting at week 10. One became azoospermic at week 16, while the other's total sperm counts continued declining and reached a nadir of 1.4 million by week 20. Sperm motility and viability in this subject were completely suppressed after week 14. Sperm counts returned to baseline levels 12-14 weeks after the end of Nal-Glu administration. The mean serum LH level of the first six subjects decreased from 3 +/- 03. U/L at baseline to less than 0.1 U/L until week 20, and then levels returned to baseline. FSH levels similarly decreased from a combined mean of 3.6 +/- 0.9 U/L at baseline to below 0.3 U/L after 4 weeks of Nal-Glu administration. Serum mean testosterone levels between weekly injections of testosterone enanthate ranged from 27.4 +/- 5.9 to 4.8 +/- 1.4 nmol/L, but remained in the hypogonadal range (less than 10 nmol/L) for 4 of the 7 days. None of the subjects, however, complained of decreased libido or potency, as assessed by a questionnaire. No systemic or significant local side-effects were observed, other than a minimal reaction at the injection site. These data suggest that complete sustained azoospermia can be achieved in man, without loss of libido, by chronic administration of a GnRH antagonist plus testosterone.

Adult↗

PubMed1990

Immunocytochemical analysis of embryonic compartmentation with a monoclonal antibody against a cytokeratin-related antigen.

Mab 113F4, a monoclonal antibody recognizing an antigen in the outer synaptic layer of the chick neural retina, also recognizes an antigen appearing in all three germ layers of the gastrulating chick embryo. However, as neurulation proceeds, the antigen is down-regulated in three distinct patterns. First, the antigen is lost specifically from those trunk ectodermal cells destined to form the neural plate and, later, the neural tube. It remains absent from any neural derivative until day 13 when it appears in the outer synaptic layer of the neural retina, coincident with synaptogenesis in this region. Second, the entirety of the head ectoderm loses this antigen as the head lifts off the blastoderm. This down-regulation is followed later by a similar loss of antigen expression in the trunk ectoderm. Third, expression in the mesoderm becomes limited to the lateral plate and extraembryonic epithelia. Endodermal derivatives continue to express the antigen throughout development. Antigen 113F4 is localized within the cytoplasm and is organized in a fibrillar pattern. The intracellular localization of this antigen and its characteristic spatio-temporal tissue distribution are consistent with the antigen being a cytokeratin or cytokeratin-related antigen. The changes in tissue distribution suggest a possible role in tissue modelling in response to inductive interactions during development.

Animals↗

PubMed1990

Intracarotid hydroxyethyl methacrylate solution causing stroke in dogs.

Hydroxyethyl methacrylate (HEMA) has been advocated as a polymerizing solution with which to prevent deflation of detachable balloons in interventional neuroradiology. It is pertinent to know if unpolymerized HEMA would have untoward effects if accidentally released into the carotid artery by balloon rupture or deflation. Seven mongrel dogs underwent transfemoral catheterization of the common carotid artery and subsequent injection of HEMA solution in volumes of 1 cc in five dogs, 2 cc in one, and 4 cc in one. Angiography performed at the time of injection revealed evidence of intravascular thrombosis as well as possible spasm. Three surviving animals were sacrificed at 48 hours; the brains were fixed and examined histopathologically. One brain was normal and one was autolyzed and could not be examined. Five of the seven animals had histopathologically documented cerebral infarctions of varying size. No foreign substance was seen within the blood vessels to suggest intravascular polymerization. The animals injected with 2 or 4 cc HEMA solution did not survive 48 hours. Literature review reveals little documentation of the toxicology of intravascular HEMA. With its increasing popularity as a compound for polymerization in detachable balloons introduced into the brain, further investigations are warranted to understand the physical properties of the compound and potential risks of its use.

Animals↗

PubMed1989

Reversible middle cerebral artery embolization in dogs without intracranial surgery.

Using dogs, we developed an intravascular model for reversible middle cerebral artery occlusion that does not involve intracranial surgery or enucleation. Using silicone plastic plugs with a suture embedded within them, we embolized the middle cerebral artery in 19 dogs via the cervical carotid artery. The free end of the suture remained accessible in the neck, and after variable dwell times traction was placed on the suture and the plug was withdrawn. Placement of the plug in the middle cerebral artery produced ischemia in the basal ganglia. The degree and distribution of cortical ischemia were variable as evidence by the pathologically documented scattered nature of infarcts that resulted when the plug was left permanently in the middle cerebral artery and when it was removed after 1 or 2 hours. Angiography demonstrated occlusion of the middle cerebral artery with the plug in place as well as reperfusion when the plug was withdrawn. This modification of a previously described model of middle cerebral artery occlusion provides an opportunity to study structural, physiologic, and biochemical events occurring in acutely hypoperfused cerebral tissue as well as critical changes leading to irreversible injury without the disadvantages of surgical manipulation required by all previous models of reversible cerebral ischemia.

Animals↗

PubMed1988

Neurosurgical treatment of intractable epilepsy.

Many patients with epilepsy are refractory to anticonvulsant therapy. For some, surgery is a means to control their seizures. Temporal lobectomy, the most common neurosurgical approach to intractable epilepsy, has resulted in improvement or cure in as many as 90% of treated individuals. To determine patients suitable for surgery, presurgical selection and evaluation criteria have been devised. With epilepsy surgery becoming more widely utilized and more centers appearing in the United States, there is a growing need for neuroscience nurses to know about recent developments. This overview of surgery for epilepsy includes the presurgical evaluation process through the postoperative phase presented from a nursing perspective.

Brain↗

PubMed1988